(a) Field of the Invention
The invention relates to a test apparatus and a test method for testing an optical device, and more particularly, to a test apparatus and a test method for generating a plurality of combinations of object distances to test an optical device.
(b) Description of the Related Art
An optical device is wildly applied in electronic devices, such as digital camera, mobile camera phone, PC camera, PDA, toy and monitor, to capture an image. The optical device includes a lens module and an image sensor such as CMOS (Complementary Metal Oxide Semiconductor) or a CCD (Charge Coupled Device). During the manufacturing and assembly process of the lens module and the image sensor, the quality of the image captured by the optical device varies with the manufacturing difference. As a result, before delivered out of the factory, the optical device should be tested and its focal length should be adjusted so that the optical device after tested can conform to the specification of original design.
FIG. 1 shows a schematic diagram illustrating a conventional light box for testing a optical device. A conventional light box 10 for testing an optical device conforms to the specification of International Standard Organization (ISO) and Standard mobile imaging architecture (SMIA). The light box 10 can test the property of an optical device 14 such as resolution, opto-electronic conversion function (OECF), gray value, modulation transfer function (MTF), spatial frequency response, etc.
Referring to FIG. 1, the light box 10 comprises a housing 11 and a target, a light source 13, a optical device 14, a host computer 15, and an screw rod 16 which are disposed in the housing 11. For testing different properties of the optical device 14, different test charts may be formed on the target 12. For example, when the resolution of the optical device 14 is measured, the test chart conforming to ISO12233 standard may be used. During the test, light from the light source 13 shed on the target 12 is reflected to the optical device 14. The optical device 14 captures an image and transmits it to the host computer 15 which analyzes the image captured.
However, when the conventional light box 10 is used to measure focusing condition or extend deep of focus or field of the optical device 14 at different object distances, the target 12 have to be moved to change the object distance thereof by means of the screw rod 16. This is time-consuming and the extend deep of focus or field may not be able to be obtained. Especially, in order to analyzes the autofocus functions and the focusing resolution, images of the target 12 captured at different object distances are required when the optical device is tested to examine its autofocus functions or to calculate its extend deep of focus or field by using application software. Since the images need to be captured at different object distances, the testing time is relatively long.